Perhaps actual developers should summarize status of KDE4 on Windows here, while we encourage users to describe their experiences on the Talk page?

KDE Installer for Windows

You can use this installer to download and install the
various binary packages that you need to run KDE applications on MS Windows.
KDE is free and open source so you can build all the applications "from scratch" from their source code;
but as a convenience for others,
volunteers create these precompiled packages and make them available on the Internet.

Disclaimer These are early days for KDE4 on Windows,
some programs work better than others and some fail to run altogether.

If you experience any problems please have a look into our mailing list.

You can also use the KDE Installer for Windows to install source code and the packages that you need to build KDE4 on Windows
(although if you are building KDE4 on Windows you may prefer to use the emerge system to build KDE and its requirements from latest source);
see Getting Started/Build/KDE4/Windows.

Try running a Qt application in the bin directory, such as linguist.exe

If that works, try running a KDE application such as kwrite.exe.

Download needed packages

For the first time when you run KDE-installer you'll see the welcome screen. Since it's your first launch - leave the checkbox below unchecked. Proceed to the next screen, where you are to choose the KDE4 installation directory. It can be any of your favor, e.g. C:\KDE4.

On the next screen you are to define who you are - End User ot a Developer. The End user installation installs only binary packages and libraries needed to run KDE application. Developer mode provides you with the source code for all packages needed to build KDE from scratch. If you have chosen to be a Developer, then you need to decide what compiler to use - MinGW or MSVC. In End User mode there're only MSVC packages currently available.

Proceed to the next screen and there you're to choose the directory where all the downloaded packages will be stored. Let it be something like C:\KDE4-tmp or C:\KDE4-packages.

The next screen will ask you to choose the type of your connection to the internet. It's usefull when you are using proxy. If you don't use proxy, then just click 'Next'. If you are unsure of whether you're using proxy or if you have web browser configured to work with it properly - choose the second or the third option, according to your favourite web-browser. If you'd like to set all the settings manually - choose the last option and go ahead.

When you click the 'Next' button the list of available servers will be loaded and you could choose the one, which is closer to you. Currently the list isn't very long, though.

If you click 'Next' again the list of all available pckages will be loaded and processed to provide you with the list of package groups that you're able to select for further installation. There short description next to each group of packages for you make your choice easier. Select the packages you need. Proceed to the next screen.

Here you can see all the required dependencies. Just click 'Next' to download them all.

After all the packages are downloaded they'll be unpacked and processed by the installer. The final window will tell that your KDE installation for windows is complete.

Issues with KDE Installer for Windows

If something goes wrong during installation, for example a file can't be replaced because it is still in use, the installer may still report successful completion. If you see any alert or failure message from the installer, when it completes quit and re-run it.
If that didn't help and you think it's a bug, please report to [2]

Testing your installation

Navigate to the bin directory.

See if you can run the Qt program assistant.exe.
Qt programs have fewer dependencies than a full-blown KDE application.

If that works, try running a simple KDE application, such as lskat.exe from the kdegames package.

Look into your start menu: there will be a new entry KDE 4.XX.XX Release. Below that folder you can find all the apps you installed.

Fine-tuning

Set Oxygen style for widgets

The default KDE widget style on Windows is the native one. You already have Oxygen style installed (which is a plugin library %KDEROOT%\lib\kde4\plugins\styles\oxygen.dll), so it can be used as well. To set it for a single user:

edit %APPDATA%\.kde\share\config\kdeglobals (for versions older than 4.0.85 use %USERPROFILE%\.kde\share\config\kdeglobals) with any text editor (e.g. kwrite) Note: `cd %UserPROFILE%` will change to the right directory, effectively telling you what %UserPROFILE% expands to, such as "C:\Documents and Settings\mark"

locate the General section (a line containing the text "[General]"). If there is no General section, create one.

Within the General section ([General]), edit the line containing widgetStyle=.... so that it reads widgetStyle=oxygen. If there is no such widgetStyle=... line, create it.

Newly started applications should be displayed with Oxygen style now.

Change the mouse to Double Click

To change the mouse to use double click:

Add a new section with a line:

[KDE]
SingleClick=false

Newly started applications (Dolphin and Konqueror) should use double click now.

Full-text search in khelpcenter does not work because Perl scripts are disabled.

Many applications have a generic icon in Windows Explorer.

Multimedia support should work, although video support might be missing(from the backend)

General notes:

There are many other KDE programs that are not part of KDE 4.0.0 and are not currently packaged for MS Windows.

By design, KDE-windows does not provide the full-blown KDE desktop, a preview on the plasma shell replacement will be available in 4.1.1 - Nevertheless this does not rely on kwin/X11 which means that desktop effects are not available

Some KDE programs use UNIX-specific features, such as konsole's use of pseudo-terminals, and thus are difficult to port to MS Windows.